1. impossible or very difficult to understand or comprehend
Usage: nonstandard; incomprehensible is preferred

Examples

• The professor’s explanation was completely ununderstandable to the students.
• His handwriting is so messy that it’s ununderstandable.
• The technical manual was written in ununderstandable jargon.
• She spoke so quickly that her words became ununderstandable.
• The ancient text remains ununderstandable without proper translation.